During the last decade, canola (Brassica napus L.) has become increasingly popular with growers in the Pacific Northwest. Problematic weeds have spurred commercial companies to developed genetically modified herbicide resistant canola cultivars by using both conventional breeding and recombinant DNA techniques. Among the concerns related to the use herbicide resistant canola is the potential transfer of resistance genes to other canola crops and to closely related weed species. This study investigates potential risks associated with herbicide resistant canola by first examining gene transfer between canola and field mustard (B. rapa L., a closely related weed species) and then determining the viability of these hybrids. One aim of this study is to examine the possibility of producing a canola-weed hybrid with multiple herbicide resistance. Canola lines resistant to one of two different herbicides—Roundup (Glyphosate) or Raptor (Imazemox)—and seed from a local population of field mustard were planted in adjacent plots in a field trial. At maturity, seed from the field mustard plots was harvested by hand threshing, and planted in seedling-flats in the greenhouse. Plants possessing 4-6 leaves were then treated with either Roundup or Raptor, corresponding to the resistant canola the field mustard was adjacent to in the field. Survivors (putative hybrids) were transplanted into 15 cm pots and sprayed once more to confirm resistance. A total of 3.0% of the hybrids screened showed resistance to Roundup, 6.0% of the hybrids showed resistance to Raptor. Only 17% of the hybrids were self-compatible, yet all hybrids indicate some degree of cross compatibility with other hybrids, suggesting that multiple herbicide resistant hybrids would be a possibility. A second year of field work is currently underway to examine the likelihood of cross-pollination between putative weed-canola hybrids and herbicide resistant canola that could result in hybrids carrying genes for resistance to two herbicides.

Key words: Brassica, GMO's, herbicide resistance, pollen transfer, putative hybrids, recombinant DNA